Process of stabilizing hydrazine and hydrazine hydrate and mixtures of either of them with alcohols or water



Patented June 1, 1954 PROCESS OF STABILIZIN G HYDRAZINE AND HYDRAZINE HYDRATE AND MIXTURES OF EITHER OF THEM WITH ALGOHOLS OR WATER Josef M. Michel and Karl F. Hagar, Fort Bliss,

Tex., assignors to the United States of America as represented by the Secretary of the Army u nudi- Claims.

The invention described herein may be manufactured and used by or for the Government for governmental purposes without the payment of any royalty thereon.

This invention relates to the stabilization of hydrazine and its mixtures with water or alcohols against the decomposition caused by contact with ll'OIl.

It is well known that anhydrous hydrazine, hydrazine hydrate and mixtures of either of them with water or alcohols are decomposed by contact with metals like iron. On the other hand, these substances are quite valuable as propellant fuels, particularly for rockets. Accordingly, a primary object of our invention is to provide means for stabilizing the above mentioned rocket propellants in the presence of iron.

It is equally well known that hydrazine and fuels containing it are very corrosive towards metals, including the iron frequently found in fuel systems. A second object of our invention is therefore provisions of means to prevent the corrosion of iron in the presence of hydrazine and mixtures thereof with water or alcohols.

Qbviously means which will simultaneously prevent the decomposition of a fuel by iron and protect iron against the corrosive action of the fuel has advantages over separate means for accomplishing the same purposes. A third object of our invention is consequently provision of a method whereby corrosion of iron by hydrazine and decomposition of hydrazine by iron are prevented at the same time.

Several methods of accomplishing the previously enumerated objects of our invention could possibly be devised, such as, for example, coating the surface of any iron exposed by hydrazine with an inert material. We have chosen, however, to prevent the decomposition and corrosion by means of a chemical to be added directly to the fuel. This chemical should not detract greatly from the calorific value of the fuel and should therefore probably be at least partly organic in nature. Consequently another object of our invention is provision of an organic chemical to prevent simultaneously the corrosion of iron and the decomposition of the above mentioned hydrazine containing fuels. Other objects of the invention will be evident hereinafter.

We have found that certain known compounds will both prevent the decomposition of anhydrous hydrazine, hydrazine hydrate and mixtures thereof with water or alcohol in contact with iron and inhibit th corrosion of iron surfaces exposed to these liquids even at the boundary be- No Drawing. Application October 20, 1949, Serial No. 122,592

(Granted under Title 35, U. S. Code (1952),

sec. 266) tween the gaseous, liquid and metal phases where corrosion is particularly heavy. These compounds have the following composition:

where R1 represents a saturated hydrocarbon radical having a chain length of from 12 to 18 carbon atoms; R2 represents an aliphatic radical of the formula .-.-.CnH2n. or an aryl radical; and R3 represents sodium, potassium and ammonium ions or substituted ammonium radicals such as aniline, cyclohexylamine or methylamine.

These compounds will not appreciably diminish the propellant properties of hydrazine because they can be used in very small amounts and, in addition, consist themselves mainly of combustible components.

The preparation of the stabilizing and anticorrosion agents of this application are described in U. S. Patent 2,225,960, granted December 24, 1940.

Our invention will be more fully understood by reference to the following examples, given as illustrative only:

EXAMPLE 1 To test the amount of decomposition in con tact with iron, the liquid to be tested was placed in a glass flask, herein referred to as the reaction flask, tightly connected through a reflux condenser with a two neck receiver containing water. The second neck of the receiver carried a glass pipe leading close to the bottom of the receiver. The outlet of this glass pipe extended into a graduated cylinder. By this means the generated gas was measured by the amount of water forced over from the receiver into the graduated cylinder. Th reaction flask was put into a heating bath, for example, an oil bath regulated by a thermostat at about 0., so that the contents of the flask would boil smoothly. By this means the necessary test time was shortened by the increase of the velocity of reaction at elevated temperature. This apparatus was used for all the comparison tests of this and the following examples.

Thirty-five cubic centimeters of anhydrous hydrazine, 94.7% NZII}, was placed into the re action flask and an iron specimen of about 2.0 square centimeters surface was put into the liquid. The progressing decomposition was shown by the water which was forced out of the receiver into the graduated cylinder during constant boiling of th contents. As may be seen in Table I 3. below, the gas generation started immediately at the. boiling point and increased constantly during the test time.

The same size of iron specimens was put into com. of anhydrous hydrazine, 94.7% N2H4, after w an addition of 1% mepasin-sulfamido-acetim acid-sodium salt has been made. The term mepasin in this description refers to a, mixture of saturated hydrocarbons with a chain length between 12 and 18 carbon atoms which was originated by the Fischer-Tropsch synthesis. In this case, as shown in Table I below, the infiuence of the inhibitor delayed the start of the gas generation for about 1 hour, and during the succeeding intervals of time the gas generation stood only as a small fraction of the gas generated during the test Without the inhibitor.

Table I Decomposition of anhydrous hydrazine by contact with iron. Gas generation of 35 com. liquid and an iron specimen of about 20 cm. surface without and with inhibitor at the boiling point of anhydrous hydrazine.

. No inhib- 17 inhib- T1me of boiling o ates) ltoiggm. 1torg ccm.

EECAMIPIE 2;

The test method of Example 1 was applied to hydrazine hydrate. Table II, given below, shows the result that an addition of 1% of octadecylsulfamido-butyric-acid-ammonium salt to the liquid decreasedthe velocity of decomposition remarkably.

Table II Decomposition of hydrazine hydrate in contact with iron: Test conditions, same as Table I.

No inhib- 1'7 inhib- T1me of boiling a itor ccm. itor ccm. (minutes) gas gas Decomposition of a mixture of anhydrous hydrazine and methanol :50 in contact with iron.

. Qonditions: same as Table I.

Time of boiling (minutes) EXAMPLE 4 Table IV Decomposition of anhydrous hydrazine, 94.7% N2I-I4, by contact with iron half-covered with liquid. Conditions. same as Table I.

- N o inhib- 17 inhib- Time of boilm 0 itor ccm. itor ccm. (minutes) gas gas EXAMPLE 5 Two test tubes each carrying 15 com. anhydrous hydrazine and an iron specimen, half dipped in the liquid, but with one containing an addition of 3% mepasin-sulfamido-acetic acidsodium salt, were kept at ambient temperature. After two days, the iron sample in the pure anhydrous hydrazine showed heavy rust above the liquid, but the sample of the test tube containing the inhibitor was only slightly aifected by the hydrazine. r

We claim;

1. The process of stabilizing against contact with iron a material selected from the group consisting of hydrazine, hydrazinev hydrate and mixtures thereof with a liquid medium selected from th group consisting of water and alcohol which comprises accomplishing said contact in the presence of a small but effective amount of a stabilizing agent of the formula in which R1 is a saturated hydrocarbon radical with a chain length of from 12 to 18 carbon atoms, R2 is an aliphatic radical of the formula -CnH2n, and R3 is a member of the group consisting of hydrogen sodium, potassium and ammonium ions, and aniline, cyclohexylamine and methylamine radicals.

2. A rocket propellant comprising a member of the group consisting of hydrazine, hydrazine hydrate and mixtures thereof with a liquid medium selected from the group consisting of water and alcohol, said propellant carrying therein a small but effective amount .of an inhibitor against the corrosion of iron and decomposition of the propellant in contact with iron, said inhibitor have the formula in which R1 is a saturated hydrocarbon radical with a chain length of from 12 to 18 carbon atoms, R2 is an aliphatic radical of the formula --C11.H2n--, and R3 is a member of the group consisting of hydrogen sodium, potassium and ammonium ions, and aniline, cyclohexylamine and methylamine radicals.

3. A rocket propellant consisting essentially of hydrazine hydrate carrying therein about 1% by weight of the ammonium salt of octadecyl-sulfamido-butyric acid.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,215,077 Beekhuis, Jr. et al., Sept. 17, 1940 2,238,651 Keenan Apr. 15, 1941 2,330,524 Shields Sept. 28, 1943 2,578,725 Michel et a1 Dec. 18, 1951 

1. THE PROCESS OF STABILIZING AGAINST CONTACT WITH IRON A MATERIAL SELECTED FROM THE GROUP CONSISTING OF HYDRAZINE, HYDRAZINE HYDRATE AND MIXTURES THEREOF WITH A LIQUID MEDIUM SELECTED FROM THE GROUP CONSISTING OF WATER AND ALCOHOL WHICH COMPRISES ACCOMPLISHING SAID CONTACT IN THE PRESENCE OF A SMALL BUT EFFECTIVE AMOUNT OF A STABILIZING AGENT OF THE FORMULA 